Answer: Set C is correct answer.
Explanation:
Symmetrical distribution is a type of distribution in which all data occurs at regular frequencies, and the measures of central tendency is occurred at same point.
Here, we can see from the options that
Set C has data with same difference i.e. 5
Here, Median would be 17 as the median is the central value after arranging the data value in ascending order.
Mean =

∴ Mean = 17
Mode = 3 Median - 2 Mean

∴ Mode = 7
Thus, all mean, median and mode is occurred at same point i.e. 7.
Hence, Set C is correct answer.